1. Field of the Invention
The invention relates to memory cards, and more particularly to a memory card detection circuit.
2. Description of the Related Art
Conventional memory cards, such as Compact Flash from ScanDisk, Smart Media from Toshiba, Memory Stick from Sony, Multi-Media from Nokia and Motorola, and Secure Digital from Panasonic are coupled to a computer through a card adapter, which adapts the interface signals of the memory card to Personal Computer Memory Card International Association (PCMCIA) standard, whereby data is transmitted to the computer for further processing or storage.
A detection circuit of a card bus controller notifies the computer when a card is coupled thereto. After the memory card type is identified, the computer directs data transmission from the card. Voltage difference between the two ends of the pins connecting the computer and the memory card generates a ground bounce in the voltages of the connection pins. The memory card detection circuit awaits a de-bounce period after which the now steady voltages of the connection pins are measured to identify the coupling and type of the memory card. The delay in voltage detection is inconvenient and impacts performance of the card bus controller.
Further, multiple counters are required to respectively calculate specific periods to control the voltage measurement. The multiple counters require a large area, complicating the design of the memory card detection circuit and increasing the manufacture cost of the card bus controller chip.